Field of the Invention
This invention relates to a process and composition for liquid deposition on a surface. In particular, compositions containing non-fluorinated photoresist polymers combined with fluorinated polymers to define containment areas for subsequent liquid printing on the surface. More particularly, a fluoropolymer-photoresist composition on a substrate surface for physical and chemical containment of organic inks deposited using liquid printing techniques. The developed fluoropolymer-photoresist defining non-wetting structures to repel organic inks away from structures and into pixel areas on the substrate. The pixel areas can contain one or more electrodes to produce electrical devices. This composition and process mitigates spreading variability of deposited ink, using both physical and chemical containment to drive ink into desired areas and away from other areas.
Description of the Related Art
An electronic device can include a liquid crystal display (“LCD”), an organic light-emitting diode (OLED) display, or the like. The manufacture of electronic devices may be performed using solution deposition techniques. One process of making electronic devices is to deposit organic layers over a substrate, also referred to as a backplane when containing electronic elements, by printing (e.g., ink-jet printing, continuous printing, etc.). In a printing process, the liquid composition, also called ink, being printed includes an organic material in a solution, dispersion, emulsion, or suspension with an organic solvent, with an aqueous solvent, or with a combination of solvents. After printing, the solvent(s) is (are) evaporated and the organic material remains to form an organic layer for the electronic device.
Devices utilizing one or more layers of organic semiconductor materials laminated with other supporting layers and sandwiched by two electrodes are used in many different kinds of electronic equipment.
Several methods for providing ink containment for OLED devices are described in the literature. These are based on containment structures, also referred to as physical containment, and surface energy discontinuities, also referred to as chemical containment, and combinations of both physical and chemical containment. Among the methods used to supply a combination of physical and chemical containment are surface treatments of the containment structures, for example with plasma fluorination using CF4 or addition of fluorinated surfactant to photoresist formulations, to lower the surface energy of the containment structure. In both instances, CF4 and fluorinated surfactant, the lowering of surface energy is ephemeral and does not survive additional processing of the substrate to produce an OLED device, such as plasma cleaning or ozone treatment. In addition, both CF4 treatment and the use of fluorinated surfactants leads to mobile fluorinated molecules on the bank surface that can enter the OLED device to negatively affect its operation. The CF4 treatment also has the disadvantage of requiring a costly extra step in manufacturing.
Another method is to use fluorinated photopolymer. Fluorinated polymers typically have low solubility in non-fluorinated solvents and as such require fluorinated solvents for processing, both as a solvent for deposition and for the developer. Besides having potential for bioaccumulation, fluorinated solvents are expensive and recycling of material is problematic.
All of these approaches suffer from drawbacks limiting the effectiveness and economics when used in the production of electronic devices. In view of the foregoing it is believed additional improvement is required to optimize containment of inks in organic electronic devices.